The role of cavitation as a mechanism of damage associates with clinical and therapeutic ultrasound, and a detailed study of the phenomena of ultrasonically induced cavitation in mammalian tissues are investigated. Studies include (1) determination of the importance of "transient cavitation" phenomena to the safe clinical application of pulsed diagnostic ultrasound systems, (2) determination of the importance of "steady cavitation" phenomena to the safe clinical application of continuous wave ultrasound systems, and (3) identification of the anatomical sites of onset of cavitation, the cavitation nuclei and the structures (on a macro or subcellulr level) first affected. The study utilizes structural and functional endpoints and contributes to the understanding of the physical mechanisms of interaction of ultrasound and biological media.